Quantum battery: Scientists use charging to balance power, stable energy delivery

A collaboration of researchers from various parts of the world has identified the fundamental limits on the reliability of quantum batteries and figured out a way to use charging as a tool to balance high power and stable energy delivery. This is likely to help develop useful quantum energy storage devices in the near future.

Quantum batteries are the next frontier in energy storage, leveraging quantum mechanics to charge, store, and release energy. As quantum technologies like computing and sensing are developed rapidly, researchers are also looking for a way other than chemical batteries to power them.

A quantum battery can use superposition to store energy in multiple states or collective charging to speed up charging. Quantum designs for batteries could also mean larger batteries that charge faster than their conventional chemical counterparts, making them much preferred for bigger applications.

Building a quantum battery

So far, scientists have only built proof-of-concept quantum batteries. These have held energy for only a few nanoseconds and microseconds, which does not have a practical use as of now, but scaling up the technology could solve a lot of problems associated with energy storage.

Much of the previous work has focused on how fast quantum batteries can be charged and how powerful they can be made. However, in a recently published study, an international team of physicists established the fundamental limits on fluctuations in energy delivered by a quantum battery and the rate at which it is delivered.

“Quantum batteries offer a fascinating link between quantum information, thermodynamics, and many-body physics. Understanding their fluctuations is essential if these systems are eventually to become useful technological resources,” said Maciej Lewenstein, a theoretical physicist at the Institute of Photonic Sciences ICFO, Spain, who was involved in the research.

What did the researchers find?

In their work, the researchers found that the well-known quantum-mechanical uncertainty relation prevents simultaneous delivery of energy and stable power. The principle that states that certain pairs of physical properties cannot be known at the same time with complete precision shows that fluctuations in energy delivery and power cannot both be made small simultaneously.

This happens because in quantum batteries, work and power are represented by non-commuting operators, much like position and momentum in quantum mechanics. The researchers further studied how this trade-off depends on the way quantum batteries are charged.

When charged in parallel, quantum cells operate independently. However, when they are charged collectively, they operate as one unit. A third approach called hybrid charging lies in between, with groups of cells interacting during charging.

Collective charging increases delivered power but also increases fluctuations, reducing power reliability. This shows that power alone is not sufficient to determine how the quantum battery will perform.

“Our results show that there is a meaningful way to balance power enhancement and the reliability of work and power,” explained Tanmoy Pandit, staff scientist at VTT, Finland, in a press release. “Intermediate-range interaction-based charging scheme can provide a useful compromise between high power and stable operation.”

The team will now investigate reliability limits in more realistic settings, including noise, dissipation, and experimentally relevant quantum systems.

The team published the research findings in PRX Quantum.